/sci/ - Science & Math

Nobody knows, it's all just mental masturbation at this point.

>>3105230
Perhaps? but like >>3105247 said its just mental masturbation

hell, for all we know there could be entire galaxies made out of antimatter

Mass dictates gravity. Think fabric and pool balls for a mental picture of gravitational attraction. The amount of mass in the universe is a mystery though I suppose.

>>3105707
What if that fabric bent more or less easily?

>>3105735
The fabric is just a place holder for the direction of attraction between two bodies.

>>3105230

One of the possibilities of the multiverse theory is that the laws of physics are different in each universe....... or at least that's what I've heard.

>>3105746
Then what if those attractions are different?

Why are those attractions the way they are? Why don't they attract more or less?

certzainly the gravitational constant might change. Some peopel speculate it might not have always been a constant.

>>3106056
Yeah, those people are fucking stupid.

>>3105230
>Could the laws of nature be 'different'?


No.

>>3106422
>>3105746

OP means "Could they have been different?"
As in, why do all the force constants and the speed of light, etc, have the values that they do.

Not sure OP, but personally I believe there are other universes with different constants. One idea I read was that by creating a black hole another universe may be created with similar or slightly modified constants, leading universes to evolve in such a way as to maximize black hole production, although I don't know how credible that idea was.

>>3106454
>beliefs based on nothing

>>3106459

>implying I don't have any basis for my beliefs just because I didn't say them in my post

http://en.wikipedia.org/wiki/String_theory_landscape

>>3106468
>but personally I believe there are other universes with different constants

Enlighten us.

>>3105230
>>3105230

stephen hawking's new book has a lot on this subject if you're interested:
http://www.amazon.com/Grand-Design-Stephen-Hawking/dp/0553805371/ref=sr_1_1?ie=UTF8&qid=13061445
63&sr=8-1

but to answer your question, yes.

physicists now think that there are many other universes out there, and each one is just a little different.

for example, the balance of forces (like you were talking about) may be altered. let's say that gravity is suddenly much stronger compared to the other forces.
this would create problems. if gravity were stronger, it would be easier for star forming clusters to form in space (which is just a bunch of interstellar matter - mostly hydrogen and a little helium - coming together). however, once a star actually formed, it would overheat and so would not live as long. this might make it very hard to sustain life if stars formed and then went to supernova every 10000 years. furthermore, if gravity were much stronger, the universe might just collapse onto itself after it 'bangs' - not very helpful for life.

on the other hand, what if gravity were weaker? also problems.
if gravity were weaker, stars might not even be able to form. and we all know that no sun means no life. a sun is the only thing we know that can provide the energy needed to sustain life. further more, planets might not even form. all in all, this is a very dark, cold, forever expanding universe.

(it's worth it to say at this point that when we say we make gravity stronger or weaker, we're talking about tweaking the value of the gravitational constant, G - or whatever constant applies to a particular force.)

<continued>

>>3106672
>>3106672

but yes, we do think that these universes do exist out there. they just obviously wouldn't have any life in them.

another thing to note is that some universes may not even have the same rules (laws) as ours!
in some there may be no such thing as an electromagnetic force. or maybe there is something that we don't have - life a new force that doesn't exist in our universe! or maybe gravity is always repulsive!


Hawking refers to the universe we live in as "in the Goldilocks region". you may be familiar with this term referring to planets orbiting at just the right distance from a star to sustain life, but here Hawking uses it in a different but similar way. he means that, in this universe, all of the fundamental forces of nature (all of her constants) are balanced just right as to give a universe that can sustain life.
physicists have actually ran simulations of universes in which the strengths of the forces were slightly different, and seen the dramatic (and deadly) affects this has on the universe.

>>3106677
>>3106677

(one more)

but now i know you're wondering why the constants in our universe have the particular values that they do.

well this is actually one of the biggest aims of string theory, to produce numbers (like the mass of the proton, etc...) from basic principles. it's true that all of these values have been measured in the lab extremely precisely, but we should be able to produce the numbers from fundamental quantities.

in the case of the proton, this can actually be done with a relatively new theory (roughly 60 years old) called Quantum Chromodynamics (QCD for short). however, the math was so hard to solve, that no one could pull out number from the damn theory. but sometime in the mid-80s a man named Constantine did just that - calculated the mass of the proton - but he used computers to do the math (using something called Lattice Theory to translate the continuous fabric of space into discrete lattice points for a computer to analyze), so he didn't have to solve the equations himself.
but it turns out that he may have fudged his numbers a bit so that he would get the correct mass for the proton.


but the value of the universe's fundamental constants should be calculable from basic principles from a theory that completely describes the phenomenon. unfortunately, this has not been done very successfully to date.
well i hope this answers your questions OP.
if you have any more questions, just direct them to your nearest me.

You can change the laws of nature, ya know.

Technically, there are no such things as laws.

It's logically possible, if that's what you mean.

>>3106672
>>(it's worth it to say at this point that when we say we make gravity stronger or weaker, we're talking about tweaking the value of the gravitational constant, G
>>we make gravity stronger or weaker
>>tweaking the value of the gravitational constant, G

I thought the gravitational constant was g? Also, how does one go about making gravity stronger or weaker without adding or removing mass?

>>3107130

g is a different constant than G.
g refers to the acceleration due to gravity close to the Earth's surface.

G refers to the overall strength of the gravitational force in general. it is the same all over the universe (which is why it is sometimes called the universal gravitational constant).

when i talk about making gravity stronger or weaker, i don't mean at all that this is possible in our universe, nor i want to adjust the masses.
what i'm doing is changing the value of G.

in general, gravity (at least Newton's gravity) is described by this law:

F = G M*m/(r^2)

where F is the force of gravity on the two masses, G is the universal gravitational constant, M and m are the two masses, and r is the distance between M and m.

you know that changing the masses will increase or decrease the force between them, but that is trivial because we're not really saying anything about the strength of the gravitational force, all we're taking about is the 2 masses.

to change the strength of gravity *everywhere* you need to adjust G, which is the only thing that makes sense.
and keep in mind that there is no way to change the value of this constant in our universe (it would be like trying to change the value of pi).
this constant (and every other constant) is determined by the universe, when the universe is born.
that is, the value of the constants in a universe - and hence, the strength of the forces - is a property of that particular universe

I remember reading an article on NewScientist or Discovery News or something about how they discovered that a fundamental constant ( which I think was called Aleph something ) varied across a gradient throughout the universe.
The interaction of light on matter was dependent on the value of this constant. But they realised that the Solar System was in a good place to maintain conditions needed for life; if this system was at some other part of the universe, the gravity of the sun would be too much or too little etc..
So I suppose the 'Laws' you're referring to can be different.

>>3105230

there is no logical reason suggesting you can't.

you might have to change more than one, since some of them might be intertwined.

but they aren't even laws, they are just regularities we interpret...no reason why they can't change tomorrow

>>3108677
http://www.space.com/9122-physics-fundamental-cosmic-constant-shifty.html
This is.

>Could the laws of nature be 'different'?

Stellar fusion, planet formation and chemistry are possible without the weak nuclear force.

http://en.wikipedia.org/wiki/Weakless_Universe

>>3106454

I will concede that it may be possible for alternate universes to exist, but to actually believe that they exist is fallacious. There is no evidence for their existence, and no evidence could ever be found for a universe outside our own.

If we could perceive any evidence, it would by definition be a part of our own universe as nothing outside of it can ever be perceived or interacted with.